A cathode active material used in a battery is an important portion for improving performance of the battery, and particularly, in order to manufacture a battery having a high-energy density and high power performance, a high-capacity cathode active material is required.
In addition to improving performance of the battery through the high-capacity cathode active material, in order to improve storage capability of the battery at a high temperature, a sulfur based additive is mainly added to and used in an electrolyte. However, in the case of using the sulfur based additive, a cycle life of the battery is decreased, and power characteristics of the battery are deteriorated. Therefore, there is a need to solve problems occurring at the time of using the sulfur based additive while using the high-capacity cathode active material to improve performance of the battery.
The development of a novel technology capable of improving performance of the battery while hardly causing a trade-off of power and cycle life characteristics in spite of using the sulfur based additive as described above has been urgently demanded.
For example, a lithium battery using an electrolyte containing a solid sulfide, in which a specific metal element concentration is high in a portion contacting a solid electrolyte has been disclosed in U.S. Patent Application Publication No. 2013-0065135. However, in most studies, these technologies are to improve performance of the battery itself, and the development of a technology for a cathode active material capable of overcoming disadvantages of the lithium battery using the electrolyte containing the sulfur based additive was not reported.